Over the years, numerous different chair designs have been developed. Several such designs have employed a pre-molded seat, with an integral back, attached to a tubular frame. Various was of attaching the tubular frame to the seat were employed. Some designs employed brackets which allowed the seat to be secured to the bracket and at the same time allowed the frame to be secured to the bracket using suitable fasteners such as screws or bolts. Illustrative of such designs are U.S. Pat. Nos. 3,904,243; 3,476,342; 3,166,030; and 2,999,662. Other designs have employed a plurality of split sleeves formed on the undersurface of the seat which were pressed onto a frame member. These split sleeves generally had a U-shaped configuration and were open at their lower end. The sleeve materials were resilient. When the seat was pressed onto the frame member the clip members parted temporarily followed by the clip members springing back to the original position and gripping the frame member. illustrative of such designs are U.S. Pat. Nos. 3,245,715 and 3,146,028. It is noted that in U.S. Pat. No. 3,146,028, the rear engagement between the seat and the fame occurs behind the back of the seat as opposed to the underside of the seat. However, the technique of using flexible engaging elements is still employed. U.S. Pat. No. 3,061,374 employs the identical technique revealed in U.S. Pat. No. 3,146,028. Another design has been to employ a frame involving interlocked and inclined legs which engage a pair of opposed open hooks in order to support a load. This design is shown in the application of a support for a portable barbecue grill as illustrated in U.S. Pat. No. 3,556,076. The legs 50 and 44 are retained in the hook member 66 and are retained in that position by an interference fit with the other side of the grill 86. A combination of a hook element with a resilient U-shaped clamping element to retain a seat to a frame is illustrated in U.S. Pat. No. 3,393,941. The '941 patent illustrates a front hook shaped support member combined with a rear U-shaped gripping member which resiliently flexes over the support bar 1b and then engages the support bar as the resilient members 2d resume their initial position. Also relevant to the apparatus of the present invention is U.S. Pat. No. 400,296 illustrating a wire clamp wherein a wire 3 is installed through a pair of opposed hook shaped members 2 in such a manner that the installation of one wire over another wire retains the two wires together.
One of the design shortcomings of using resilient U-shaped clip members to resiliently flex over a support member and then spring back to their original shape, is that only a limited amount of gripping force is available to retain the seat to the frame. In the design of the '941 patent, which employs the hook shaped member in the front of the seat and the inverted U-shaped clip member in the back of the seat, the entire back of the seat can be dislodged from the frame if a sufficiently large load is applied to the very front of the seat. Similarly, when such chairs of the design of the '941 patent are being handled in normal use, a significant load applied from the rear of the back rest toward the front of the seat with the frame restrained will also potentially dislodge the connection 2d at the rear of the seat.
It is thus desirable to provide an attachment system that is economical to manufacture and has the desirable properties of maintaining a secure engagement between the frame and the seat. Another desirable feature is to provide the above-recited features in combination with an upholstered seat. In using an upholstered seat, it is desirable to secure the edge of the upholstery fabric out of sight of the person viewing the chair. In that manner, the aesthetic features of the chair are accentuated without any distraction from fasteners between the upholstery and the seat. Some designs have applied a visible welt to the periphery of the upholstery to secure the upholstery to the seat. Illustrative of such designs are U.S. Pat. Nos. 4,558,904; 2,151,628; and 3,273,178. Other designs have employed a pronounced peripheral casing around the seat which included a mechanism for attaching the edges of the upholstery to the seat. Illustrative of such design is U.S. Pat. No. 2,551,084. Other designs have employed an elongated profile strip which has its ends specifically designed to engage a recess in the underside of the seat for the purposes of retaining the cushion and upholstery covering to the seat. Illustrative of such design in U.S. Pat. No. 4,408,797. Yet another method of securing the upholstery to the shell is to employ a retaining element having a substantially circular cross-section with an extending finger therefrom. The fabric ends are rolled around the finger and then snapped into a peripheral C-shaped retaining track. Illustrative of such designs are U.S. Pat. Nos. 4,357,723 and 4,465,534. Other designs have employed a recessed groove with a welt cord disposed therein. The welt cord was attached into the groove by means of a staple. Alternatively, an adhesive was used to hold the edge of the fabric to the welt before the welt was fitted into the mounting groove. Illustrative of such design is U.S. Pat. No. 4,370,002.